1. Technical Field
The present invention relates generally to a liquid additive injection pump for injecting a predetermined amount of a secondary fluid into a primary fluid stream, said pump driven by a fluid powered motor. More specifically, the present invention relates to a liquid additive injection pump having an external mixing chamber separated from the fluid-powered-motor components by a one-way valve gasket assembly.
2. Description of Related Art
Fluid powered motors driving an additive injection pump connected to a source of fluid additives are typically installed in a line containing primary fluid under pressure. The primary fluid produces reciprocating movement of a piston assembly within a housing of the fluid motor. The fluid motor in turn reciprocates a piston within a cylinder of the additive injection pump to draw a quantity of secondary fluid into the primary fluid. Such devices have been applied to add medication to drinking water for poultry and livestock, treat water with additives, add fertilizer concentrate to irrigation water, or add lubricant or cleaning agents to water. In liquid additive injection pumps, such as that shown in U.S. Pat. No. 4,558,715, reciprocating movement of the piston assembly is produced by a valve mechanism operable to establish a differential pressure. Specifically, opening and closing of the valve mechanism synchronized to the upstroke and down stroke positions of the piston assembly produces a pressure differential that moves the piston through its reciprocating cycle. Opening and closing of the valve mechanism is synchronized to the piston assembly by an over-center mechanism, which is actuated coincident with the piston assembly reaching the ends of its upstroke and down stroke positions. The over-center mechanism is spring-biased and serves to toggle the valve mechanism open and closed when an actuating shaft carried by the piston assembly engages stops that define the ends of its upstroke and down stroke excursions.
Certain fluids, however, can be quite corrosive, and still others may cause corrosive or otherwise harsh chemical reactions when mixed with a second fluid. Corrosive fluids and harsh chemical reactions can damage the pumping elements. Thus, a need exists for a differential-pressure piston-type fluid injection pump having a separate mixing chamber downstream of the pumping/metering elements. Furthermore, a need exists for a simple mechanism for preventing backflow from the separate mixing chamber into the pumping/metering elements.
Further objects of this invention will be apparent to persons knowledgeable with devices of this general type upon reading the following description and examining the accompanying drawings.